The historical novel has never been so popular. And if Hilary Mantel's recent Booker win for Wolf Hall, set in the Tudor England of Henry VIII and Thomas Cromwell, represented the genre's more literary wing, then Robert Harris is her blockbuster equivalent. He has taken on the Second World War in the code-cracking thriller Enigma and crafted hugely enjoyable what-if dramas in which Germans win the war (Fatherland) and Stalin's son readies himself for a return to power (Archangel). They have all sold millions. His new book is Lustrum, the second in a trilogy on the famous Roman statesman Cicero. All this comes after perhaps his most satisfying book, Pompeii, on the eruption of Vesuvius. Does such fascination with the past reflect Harris's interests, or that of the world as a whole?
"I think it might be a coincidence that there are so many successful books with historical themes right now," he tells me. "But I do think it might be easier to take a step back and write about the past in a way that perhaps does reflect on what we think today. Things change so quickly now that a novel about contemporary times appears out of date the moment you think of it, let alone write it and get it in the bookshops. Hilary Mantel made a very good point when she was asked why she hadn't thought about writing about the world in 2009. She said that contemporary writing was done by journalists, not novelists."
Harris should know: he was once the political editor of The Observer. From the moment we start talking, it is obvious that the political flame burns bright. Most of the conversation we have in his car while speeding between two English towns for book signings isn't directly about Lustrum at all, but about government, politicians and power. The themes obsess him, which is why it seems apposite to begin right at the beginning of the book. Most newspapers have speculated that Lustrum's dedication "For Peter" is to the infamous UK first secretary of state, Peter Mandelson, who has twice had to resign from the British government under embarrassing circumstances.
"Absolutely, I don't mind confirming it's him," Harris says. "In the 25 years of knowing Peter, I've talked about politics constantly with him, and I've also learnt an enormous amount from him. It's not meant to imply that any of the characters are meant to be him, but it was a way of acknowledging that through him I've come to understand the way politics is played. So I rang him and said: 'Shall I dedicate this book to you? I don't want to embarrass you.' And he said: 'Robert, I am beyond embarrassment.'"
Nonetheless, commentators have had great fun joining the dots and finding the parallels between Roman and contemporary politics. Indeed, anyone reading this propulsive second instalment of the Cicero story would find it difficult not to raise an eyebrow when laws are passed to prevent government officials from abusing their expenses. "I know," Harris smirks. "Incredible really - and of course I wrote that section long before what happened this year. But it just proves that these things go on and on."
And they began with the Roman republic. Lustrum is a gripping read, starting in the vein of a complex thriller as Cicero, the consul-elect and therefore the head of government, comes across the mutilated body of a child in 63BC. The expectation is that the book will embark upon a murder mystery, but Harris not only stays true to the history but to his first love, the politics of the time. A few chapters later, Cicero finds that the boy was a sacrificial seal on an oath by his rival Catilina to murder him and take control of the state. In the background he has other rivals and allies: Caesar, the great general Pompey, the money-fixated Crassus, the politicking Cato and the playboy Clodius. As Cicero battles with the horrors and realities of power, he has to play these figures off against each other in the constant knowledge that failure in politics at that time meant death or exile.
"Absolutely, and one of the main reasons for writing about politics in that era is that it was so much more interesting. The stakes were higher - I really think it was one of the most dramatic periods in human history: just read the names out alone and they conjure up all sorts of images." The double benefit is that by recreating that dramatic past, Harris can shine a light on the present. "That's what drew me to it," he affirms. "It was a way of writing about politics in a universal way. If you try to do that by inventing an MP, a constituency and a prime minister, it feels very earthbound and parochial. But if you're writing about Rome, wherever you are in the world it has in some way affected your politics.
"And the way the Roman system was set up is easier to relate to. Their laws, the politics, the technology, the logic, the literature... every generation rediscovers Rome and feels the closeness of it. It has an almost religious charge: if you go to Rome or read the history you completely feel that people thousands of years before us thought as we think and lived their lives in remarkably similar ways. It's a very powerful notion."
By that rationale, it's easy to relate to Cicero's concerns, not least because his slave-secretary Tiro wrote most of them down. So when Cicero wearily says that the problems of the state are unsolvable, and that people get tired of governments, I wonder whether those are Harris's beliefs, too. "Broadly, yes. The cliché coined by Enoch Powell that all political careers end in failure is true. But politicians collude in this: they like to present themselves as people who are going to make the world a better place. Then when they fail to do this after five, 10 or 15 years, they get thrown out and replaced by other people, who are swiftly reviled also, and the system goes on. But some things can never be fixed. The war on crime can never be won, can it? These problems go on and on, and so what inevitably happens is that people get bored with governments and want to try someone else."
It doesn't take much to nudge Harris into talking about contemporary politics, and even when I mention Cicero's main claim to fame - his legendary speechmaking skills, which are adeptly evoked in Lustrum - he immediately laments that such theatre has disappeared. I remind him of Barack Obama's brilliant inauguration speech from earlier this year in front of a crowd of millions, but it is dismissed as the exception that proves the rule.
"In Roman times and in Britain in the 18th and 19th centuries, even with people like Lloyd George and Winston Churchill, we had speakers who could leave you spellbound. Now it seems there's only Obama in the whole world who can get to that level. I truly believe that he speaks in a way that Cicero and the ancient Romans would have understood, but otherwise, it's dull. All the fun has gone out of politics."
The fun we do get these days is watching politicians squirm their way through scandals and unpleasant headlines. Harris found himself on the receiving end recently when he publicly came out in support of Roman Polanski. The film director was arrested in Switzerland last month and put in provisional detention at the behest of the United States after fleeing America in 1977. He'd been charged with a number of offences against a 13-year-old girl. Surely this was a matter of defending the indefensible? As I'm asking the question, I'm positive that the amiable direction of our conversation is about to come to a swift end, so it's surprising when Harris speaks in the same open way he used when talking about Mandelson.
"Look, of course I expected a certain level of criticism because I wrote about it in a major newspaper," he says. "But I know him. My children know him." The argument, though, is that just because he's an artist loved by the liberal elite, who has made great films such as The Pianist, and just because 32 years have passed, doesn't mean that Polanski is above the law. "I understand that. The way I see it, there was a terrible moment of madness which I don't condone in any way, but it was judged not worthy of a custodial sentence in 1977, and he fled America because the judge decided not to honour a plea bargain. So I think it's a cruel and unusual punishment for a man of 76 to be in jail in this way. So I'm happy to stick up for him. I'm sorry if it offends people but I'm afraid I shall continue to do so."
And the reason, you feel, that Harris will continue to stick up for Polanski is that beyond being friends, their relationship has resulted in some of Harris's best work. What he describes as their "full-on" collaboration over the film adaptation of Harris's 2007 book The Ghost - which Harris believes Polanski will finish from his prison cell if necessary - led to a kind of re-evaluation of his writing.
"Roman knows a lot about telling a story. He's obviously a great director but very shrewd about writing," Harris says. "It did come to a point where I was writing a chapter in Lustrum and I could hear him in my head saying: 'No, you're leaving that scene too early.' More than any other person I have learnt from him. We're kindred spirits in that we like to make things that are entertaining, that can hook an audience, but also have something behind all of that to grab hold of.
"I want people to make a connection with Cicero and the Roman republic, to realise that the world we live in was forged in that era, and that they aren't just dusty figures from textbooks. Having said that, I did take a very conscious decision to be true to the facts and the period and not labour any parallels with today. "I was never going to twist the historical facts so that the reader could go: 'Ooh look, there's Tony Blair, here's George Bush.' You create the world of the novel primarily to entertain people, and hopefully readers respond to the characters within it. But if Lustrum makes people look at the way politics is played, how we apportion power, what kind of people are drawn to it and what we expect of them, then I will be very happy. It's a subject that's fascinated me all my life."